Yahoo Japan, the country's biggest Internet portal and 42.6 percent owned by SoftBank, said on Thursday its new Y!mobile service would aim for more than 20 million users and would use a simple pricing structure to attract new customers.

The purchase, scheduled for June 2, will immediately follow eAccess' planned merger with wireless provider Willcom, another SoftBank subsidiary. The two currently have about 10 million users combined.

Yahoo Japan President Manabu Miyasaka said the company wanted to have control of its own network, rather than using the network of SoftBank or another provider.

"We want 10 million (additional users), and we won't reach that unless we have control over our own handsets, service plans and sales channels, so we're launching this as a standard mobile operator," he told a news conference.

SoftBank's 99.68 percent stake in eAccess carries only 33.29 percent voting rights due to regulatory restrictions and therefore lacks veto control over major decisions. But it nonetheless confers effective operating control since the remaining voting rights are split among several holders.

SoftBank, which launched the Apple Inc iPhone in Japan and last year acquired No. 3 U.S. mobile carrier Sprint Corp, expects to post a special gain on the eAccess sale of 55.7 billion yen for the fiscal year ending March 2015.